The present invention relates to a nonwoven material produced by hydro-entanglement of a wet- or foam-formed fibre web.
Hydro-entanglement or spunlacing is a method which was introduced in the 1970s, see for example Canadian patent no. 841,938. The method involves forming either a dry-laid or wet-laid fibre web, whereafter the fibres are entangled by means of very fine water jets under high pressure. A plurality of rows of water jets are directed towards the fibre web which is carried on a moving wire. The entangled web is thereafter dried. Those fibres which are used in the material can be synthetic or regenerated staple fibres, e.g. polyester, polyamide, polypropylene, rayon and the like, pulp fibres or a mixture of pulp fibres and staple fibres. Spunlace material can be produced to a high quality at reasonable cost and display high absorption capability. They are used inter alia as wiping materials for household or industrial applications, as disposable materials within health care, etc.
The pulp fibres used in spunlace materials are mainly chemically exposed softwood pulp from different kinds of wood. The use of chemically exposed hardwood pulp and pulp produced from recycled fibres is also described in the literature, see EP-A-0,492,554.
Chemical pulp is produced by impregnating wood chips with chemicals and by subsequent boiling of the chips so that lignin, resins and hemicellulose are transferred to the boiling liquid. When the boiling is completed, the pulp is filtered and washed before it is bleached. The lignin content of such pulp is very close to zero and the fibres, which essentially consist of pure cellulose, are relatively long and slender. The fibres show a certain degree of flexibility, which is an advantage when the fibres are entangled by the hydro-entanglement process. Furthermore, the cellulose in the fibres form hydrogen bonds, which increases the strength of the finished material. A high degree of hydrogen bonding of the material does, however, impair the softness and decrease the bulk of the material.